1. Field of the Invention
The present invention relates to a display device such as liquid crystal display device, and particularly relates to a capacitance-type touch sensor that may be inputted with information by contact or approach of a user with a finger, and to a display device having such a touch sensor.
2. Description of Related Art
A display device is recently noticed, in which a contact detector, so-called touch panel, (hereinafter, called touch sensor) is directly attached onto a liquid crystal display device, and various button images are displayed on the liquid display device as a substitute for typical buttons so as to enable information input. In a trend of increase in size of a screen of a mobile device, this technique provides a great merit of space saving or reduction in number of components because a display arrangement may be combined with a button arrangement. However, the technique has had a difficulty that a touch sensor is attached and total thickness of a liquid crystal module is thus increased. Particularly, in a mobile device application, the following difficulty has occurred: since a protective layer is necessary for preventing scratches on the touch sensor, a liquid crystal module tends to be increased in thickness contrary to a trend.
Thus, for example, Japanese Patent Application Publication No. 2008-9750 proposes a liquid crystal display element with a touch sensor, on which a capacitance-type touch sensor is formed, for reducing thickness. In the liquid crystal display element, a conductive film for a touch sensor is provided between an observation-side substrate of a liquid crystal display element and a polarizing plate for observation disposed on an outer surface of the substrate, and the capacitance-type touch sensor using an outer surface of the polarizing plate as a touch surface is formed between the conductive film for a touch sensor and the outer surface of the polarizing plate.